Adding fault-tolerance to algorithms for weak consistency

As the number of processors increases, so does communication latency and the probability of component failure. A technique that addresses these problems is data replication, which provides faster access and greater availability. Its drawback is that the replicas must be kept consistent. The author describes a family of fault-tolerant algorithms for maintaining the consistency of cacheable data. Processors specify the consistency requirements, strong or weak, of their shared data. Data are kept consistent by a fault-tolerant multicast protocol. The protocol ensures the reliable delivery of operations on strongly consistent data. Weakly consistent data updates are inserted as operation prologues. Depending on the consistency policy, the execution of an operation causes cached data to be either invalidated or updated.<>